A Pilot Study On Pathogenesis Of Glucocorticoid-induced Ocular Hypertension After Laser Keratorefractive Surgery

ObjectiveTo study the pathogenesy of glucocorticoid-induced ocular hypertension(GIOH) in patients after laser keratorefractive surgery(LKRS),by analyzing retrospectively the incidence and clinical related factors of GIOH,investigating their variations of total tear protein and tear protein compositions,and detecting polymorphism changes within glucocorticoid receptor(GR) gene.MethodsThe whole experiment is consisted of 3 parts as follows.The 1^st part Analysis of the incidence and clinical related factors of GIOH in patients after LKRS2060 subjects after LKRS were recruited in our retrospective study to assess the incidence of GIOH;by logistic regression analysis,data of GIOH group and normal group were collected to analyse the association between GIOH and age,sex,right/left eye,max saggital diopter,max saggital curvature,depth of cut,papilla cup/disc ratio of ocular fundus and preoperative intraocular pressure.The 2^nd part Tear protein variations in patients with GIOH after LKRSSubjects10 subjects respectively in preoperative group,postoperative groups including of the 1st week with dexamethasone(DEX),the 1st week with fluorometholone(FML),the 1st month and the 3rd month;23 subjects with GIOH after LKRS.Methods1.5ul basal tear was collected by capillary tube method and stored at -20℃.2.Measurement of total tear protein with BCA kit.3.Variation of tear protein compositions by Bio-Rad image analysis system after SDS-PAGE. The 3^rd part Polymorphism analysis of GR geneSubjects:266 healthy individuals in Chongqing,39 patients with GIOH and 37 patients with normal intraocular pressure(IOP) after LKRS,12 patients with POAG.Methods:1.1ml peripheral venous blood was collected and genomic DNA was extracted from the whole blood.2.Genotyping:first,PCR primers were designed according to SNP within GR gene and suitable restriction enzymes were selected for PCR amplification,then genotyping of GR gene was finished in healthful subjects in Chongqing region,at last each SNP frequency was assessed.3.Hardy-Weinberg equilibrium assay4.According to SNP results from healthy population,genotyping of GR gene was done by BclⅠand N363S SNPs in subjects with GIOH and normal IOP after LKRS,and patients with POAG.5.Hardy-Weinberg equilibrium assay of all groups.6.Incidences of 2 kinds of SNPs were calculated,and then differences among groups and associations between these SNPs and GIOH,POAG were assessed.Results1.Incidence of GIOH after LKRS is 3.5%and is associated with C/D ratio of optic nerve head.2.Total tear protein level in postoperative group at 1^st week with DEX is higher than other groups;its variation tendency in GIOH group at different time is same to group with normal IOP.3.Tear lysozyme and lactoferrin level in patients with GIOH is higher.4.There is no ER22/23EK and N363S polymorphism of GR gene inChongqing's healthy population,but BclⅠSNP exists and its G allele frequency is 23.5%.All groups in this study are in line with H-W equilibrium. 5.The incidence of BclⅠSNP of GR gene is 21.62%and 18.57%respectively in group of normal IOP and GIOH after LKRS. 6.The incidence of N363S and BclⅠSNP of GR gene is 0 and 18.57%respectively in group of POAG,and there is no significant difference with other groups. ConclusionIncidence of GIOH after LKRS is 3.5%and is associated significantly with C/D ratio of optic nerve head;total tear protein level in patients at early postoperative period increased but decreased when GC changed from DEX to FML.So we suppose this is induced by strong anti-inflammatory,anti-immunization and effects on mesenchymal tissue of DEX;We also found tear lysozyme and lactoferrin level in patients with GIOH after LKRS improved,which maybe caused by tear secretion changes of patients with GIOH.The Chongqing population hasn't polymorphisms of ER22/23EK and N363S location but has BclⅠSNP,which is different from Caucasian but same to Japanese in the Asia. However,SNP frequency of BclⅠin Chongqing population is lower than Caucasian's. There is no difference in SNP frequency of N363S and BclⅠamong patients with and without GIOH after LKRS and with POAG.Although SNPs of N363S and BclⅠwithin GR gene has been reported to be associated with increased sensitivity to GC,no statistical association was found between these two SNPs and GIOH.Maybe there are some other SNPs associated with GIOH,which needs further research.